Supporting Information for Active Pt 3 Ni (111) Surface of Pt 3 Ni Icosahedron for Oxygen Reduction

Transcription

1 Supporting Information for Active Pt 3 Ni (111) Surface of Pt 3 Ni Icosahedron for Oxygen Reduction Jianbing Zhu,, Meiling Xiao,, Kui Li,, Changpeng Liu, Xiao Zhao*,& and Wei Xing*,, State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, , China University of Chinese Academy of Sciences, Beijing, , China Laboratory of Advanced Power Sources, Changchun Institute of Applied Chemistry, Changchun, Jilin, , China & Department of applied physics and chemistry, The University of Electro-Communications, Chofugaoka Chofu, Tokyo, , Japan xingwei@ciac.ac.cn; xiaozhao@uec.ac.jp 1

2 ORR Measurements Firstly, 2 mg synthetic Pt 3 M/C catalysts were dispersed into 1 ml water/isopropanol/nafion solution (containing 400 µl water, 550 µl isopropanol and 50 µl 5 wt % Nafion solution) by sonication. 10 µl of the dispersion was dispersed on a glassy carbon rotating ring-disk electrode (RRDE, the ring material is Pt), then dried in air. Prior to ORR test, working electrodes were pre-treated by potential cycling in the range of V (50 mvs -1, 50 cycles) to remove surface contaminant. The electrochemically active surface area (ECSA) was estimated by H upd and CO stripping experiments. For H upd calculation, the average charge of the Pt-hydrogen adsorption/desorption region after correction for double layer charging and assuming the value of 210 µc cm -2 for the oxidation of a monolayer of hydrogen 1-3. For CO stripping voltammetric experiments, CO was absorbed at 0.02 V for 10 min, excess CO in the electrolyte was then purged out with N 2 for 10 min, and then first two cycles recorded at 20 mv s -1 and assuming the value of 420 µc cm -2 for the oxidation of a monolayer of carbon monoxide. RRDE measurements were conducted by liner sweep voltammetry (LSV) from 0.2 V to 1.1 V (5 mv s -1, 1600 rpm), while the potential of ring electrode was held at 1.3 V. The following equations were used to determine the electron transfer number (n) and the hydrogen peroxide yield (%H 2 O 2 ). = 4 +( / ) % =100 2 / +( / ) (1) (2) I D and I R are the disk and ring currents, respectively. N represents the collection 2

3 coefficient of H 2 O 2 on the Pt ring. Kinetic current (I k ) was calculated according to the Koutechy-Levich equations: 1 = (3) =0.62nAFC (D ) / ν (4) in which n is the electron transfer number; F is Faraday's constant (96,485 C mol -1 ); A is the area of the electrode (0:196 cm 2 in this work); D 0 is the diffusion coefficient of O 2 in 0.1M HClO 4 (1: cm 2 s -1 ); ν is the kinematic viscosity of 0.1M HClO 4 ( cm 2 s -1 ), and C 0 is the concentration of molecular oxygen in 0.1M HClO 4 solution ( mol cm -3 ) 4. Accelerated durability test (ADT) were conducted by potential cycling from 0.6 to 1.2 V for 20,000 cycles in an N 2 -saturated 0.1M HClO 4 solution at 50 mvs -1. Specific and mass activities were obtained by normalizing the kinetic current density (calculated from the Koutecky-Levich equation) to the mass and ECSA of Pt, respectively. 3

4 Figure S1 (a) XRD and (b) XPS patterns of Pt/C, Pt NI and Pt 3 Ni catalysts. 4

5 Figure S2 UV vis absorption of Ni 2+ + Pt 4+ + glunh 2 + H 2 O solution with different reacting temperature. 5

6 Figure S3 Bright-field TEM images of Pt3Ni nanoparticles obtained from hydrothermal synthesis with different reaction temperature, (a) 140 oc (b) 160 oc, (c) 180 oc, (d) 200 oc. 6

7 Figure S4 Typical TEM (a), HRTEM (b) and HAADF-STEM (c) images of Pt NI icosahedra 7

8 Figure S5 TEM, HRTEM and HAADF-STEM images of Pt 3 Fe (a-c), Pt 3 Co (d-f) and Pt 3 Cu (g-i) icosahedral. 8

9 Figure S6 EDX, EDS line scan and corresponding elements mapping elements mapping of Pt 3 Fe icosahedral. 9

10 Figure S7 EDX, EDS line scan and corresponding elements mapping elements mapping of Pt 3 Co icosahedral. 10

11 Figure S8 EDX, EDS line scan and corresponding elements mapping elements mapping of Pt 3 Cu icosahedral. 11

12 Figure S9 TEM images of Vulcan XC-72 supported catalysts; (a) Pt NI/C; (b) Pt 3 Fe/C; (c) Pt 3 Co/C; (d) Pt 3 Ni/C and (e) Pt 3 Cu/C. 12

13 Figure S10 XRD patterns of Pt 3 Fe, Pt 3 Co and Pt 3 Cu catalysts. 13

14 Figure S11 XPS spectra of Pt 4f for Pt/C, Pt 3 Fe/C, Pt 3 Co/C and Pt 3 Cu/C catalysts. 14

15 Figure S12 XPS spectra for (a) Ni 2p, (b) Fe 2p, (c) Co 2p and (d) Cu 2p. 15

16 Figure S13 CO-stripping voltammograms of the (a) Pt/C, (b) Pt NI/C, (c) Pt 3 Ni/C, (d) Pt 3 Fe/C, (e) Pt 3 Co/C and (f) Pt 3 Cu/C catalysts in 0.1 M HClO 4 solution at a scan rate of 20 mvs

17 Figure S14 (a) Cyclic voltammetry curves of Pt 3 Fe/C, Pt 3 Co/C and Pt 3 Cu/C catalysts, (b) ORR polarization curves for Pt 3 Fe/C, Pt 3 Co/C and Pt 3 Cu/C catalysts in O 2 -saturated 0.1M HClO 4 at room temperature, with rotation rate, 1,600 r.p.m. and sweep rate, 5mVs -1. (c) Comparison of mass activities for Pt 3 Fe/C, Pt 3 Co/C and Pt 3 Cu/C catalysts at 0.95 and 0.9 V. (d) Comparison of specific activities (I k ). 17

18 Figure S15 Comparison of specific activities for Pt/C, Pt NI/C, Pt 3 Ni/C, Pt 3 Fe/C, Pt 3 Co/C and Pt 3 Cu/C catalysts at 0.9 V. 18

19 Figure S16 percentage of peroxide (black line) and corresponding electron transfer number (n) obtained from for rotating ring currents on the RRDE: (a) Pt/C, (b) Pt NI/C, (c) Pt 3 Ni/C, (d) Pt 3 Fe/C, (e) Pt 3 Co/C and (f) Pt 3 Cu/C. 19

20 Figure S17 TEM image of Pt 3 Ni/C catalyst after ADT test. 20

21 Figure S18 Pt 4f XPS spectra of Pt3Ni/C catalyst before and after ADT. 21

22 Figure S19 Cyclic voltammetry curves of (a) Pt NI/C (b) Pt 3 Fe/C, (c) Pt 3 Co/C and (d) Pt 3 Cu/C catalysts in N 2 -purged 0.1M HClO 4 solution at room temperature for various numbers of potential cycles. 22

23 Figure S20 Comparative ORR activities of (a) Pt NI/C,(b) Pt 3 Fe/C, (c) Pt 3 Co/C and (d) Pt 3 Cu/C catalysts before and after 20,000 potential cycles. 23

24 Figure S21 Mass activity of the Pt/C, Pt NI/C and Pt 3 M/C catalysts after 20,000 potential cycles at 0.95 and 0.9V. 24

25 Table S1 Elements content of the Pt 3 M (M= Ni, Fe, Co, Cu) Sample XPS / at% ICP-OES / at% M a Pt a M a Pt a M b Pt b Pt 3 Ni Pt 3 Fe Pt 3 Co Pt 3 Cu a) The initial elements content of Pt 3 M; b) After ADT test. 25

26 Table S2 Sum of electrocatalystic performance for Pt 3 M catalysts ECSA/m 2 /g Potential / V Activity@0.9V Tafel Slop H upd CO stripping E onset E 1/2-1 MA/ Amg Pt SA H /Acm -2 SA CO /Acm -2 mv dec -1 Pt 3 Ni/C Pt 3 Fe/C Pt 3 Co/C Pt 3 Cu/C Pt NI/C Pt/C

27 REFERENCES (1). Lim, B.; Jiang, M.; Camargo, P. H.; Cho, E. C.; Tao, J.; Lu, X.; Zhu, Y.; Xia, Y. Pd-Pt Bimetallic Nanodendrites with High Activity for Oxygen Reduction. Science, 2009, 324, (2). Schmidt, T.; Gasteiger, H.; Stäb, G.; Urban, P.; Kolb, D.; Behm, R. Characterization of High surface area Electrocatalysts Using a Rotating Disk Electrode Configuration. J. Electrochem. Soc. 1998, 145 (7), (3). Wittkopf, J. A.; Zheng, J.; Yan, Y. High-Performance Dealloyed PtCu/CuNW Oxygen Reduction Reaction Catalyst for Proton Exchange Membrane Fuel Cells. ACS Catal. 2014, 4 (9), (4). Jirkovský, J. S.; Halasa, M.; Schiffrin, D. J. Kinetics of Electrocatalytic Reduction of Oxygen and Hydrogen Peroxide on Dispersed Gold Nanoparticles. PCCP 2010, 12 (28),